Don't redefine _FORTIFY_SOURCE

The macro _FORTIFY_SOURCE might be already defined by environment in
which case it shouldn't be overriden (might be if it has lower value).

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Get rid of gnulib error

Even though this doesn't stop the compile phase, I find it a bit
distracting that this is what I get with bootstrap:

../.gnulib/gnulib-tool: *** cannot find ./configure.ac - make sure you
run gnulib-tool from within your package's directory
../.gnulib/gnulib-tool: *** Stop.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>